feat: allow custom input provider, removing dressing.nvim (#2173)

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>
Co-authored-by: yetone <yetoneful@gmail.com>

lua/avante/ui/input/providers/snacks.lua

@@ -0,0 +1,23 @@
+local M = {}
+
+---@param input avante.ui.Input
+function M.show(input)
+  local ok, snacks_input = pcall(require, "snacks.input")
+  if not ok then
+    vim.notify("snacks.nvim not found, falling back to native input", vim.log.levels.WARN)
+    require("avante.ui.input.providers.native").show(input)
+    return
+  end
+
+  local opts = vim.tbl_deep_extend("force", {
+    prompt = input.title,
+    default = input.default,
+  }, input.provider_opts)
+
+  -- Add concealing support if needed
+  if input.conceal then opts.password = true end
+
+  snacks_input(opts, input.on_submit)
+end
+
+return M